1. Field of the Invention
The present invention relates to novel processes for preparing cyclopentenones of Formula I,
which are useful for the preparation of the corresponding benzindene Prostaglandins. The invention also relates to novel cyclopentenones prepared from the processes.
2. Description of the Prior Art
Benzindene prostaglandins are known to be useful to treat a variety of conditions. Cyclopentenones of Formula I
wherein P1 is a protecting group for the phenol group, which are also disclosed in the co-pending patent application filed on the even date and entitled “INTERMEDIATES FOR THE SYNTHESIS OF BENZINDENE PROSTAGLANDINS AND PREPARATIONS THEREOF,” are key intermediates for the synthesis of benzindene Prostaglandins. Racemic or optically active cyclopentenones of Formula I were not disclosed in the prior art. As shown in the following Scheme 1, Sato disclosed in J. Org. Chem., 59, 21, 6153 (1994) optically active cyclopentenones of Formula B and a process for preparing the same:

However, this preparation process yielded as low as 10%. Moreover, the starting material of Formula A used in this preparation is costly and not easy to obtain as it normally would be obtained from a 11-step synthesis process starting with the expensive D-erythro-Pent-1-ental of Formula C as shown in the following Scheme 2 [J. Org. Chem., 53, 23, 5590 (1994); JP 07252276].

There has been a demand for a process for the preparation of the cyclopentenones of Formula I that involves less steps and is more convenient to operate.